圆柱齿轮传动的对制造和安装时的精度要求分为 三方面。
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国家标准规定了圆柱齿轮传动的精度等级有 级,常用精度等级是级为等精度等级。
Banked clozeFill in the blanks by selecting suitable words from the word bank. You may not use any of the words more than once.World War II was a global war that was under way by 1939, and ended in 1945. It involved a vast majority of the world's nations, including all of the great powers, eventually forming two opposing military alliances: the Allies and the Axis (轴心国). It was the most 1)_____and widespread war in human history, with 2)______people serving in military units. In state of "total war", the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing (消除) the 3)______between civilian and military resources. Estimates for the total number of 4)_____of the war vary, because many deaths went 5)______. Most suggest that some 60 million people died in the war. Many civilians died because of disease, starvation, and 6)_______.The war ended with the total victory of the Allies over the Axis in 1945. World War II altered the political alignment (结盟) and social structure of the world. The United Nations was established to 7)_______international cooperation and prevent future conflicts. The Soviet Union and the United States emerged as rival superpowers, setting the 8)_______for the so-called Cold War, which lasted for the next 46 years. Meanwhile, the influence of the European great powers started to 9)__________, while the decolonization (非殖民地化) of Asia and Africa began. Most countries whose industries had been damaged moved toward economic recovery. Political integration, especially in Europe, emerged as an effort to 10)_____post-war relations.
在核酸中占9%~10%,且可用于计算核酸含量的元素是:
A. C
B. N
C. O
D. P
E. H
核酸的基本组成单位是:
A. 核糖和脱氧核糖
B. 单核苷酸
C. 戊糖和碱基
D. 磷酸和戊糖
E. 磷酸、戊糖及碱基